Any simple(ish) way to warp a .png?
I guess one of the easiest way will be to use shapekeys, but it requires a bit of knowledge (I would personally prefer bones but it needs to know a bit of rigging). If I make it short:


Create your tree image. Save it as a PNG with transparent background. Import your image as a background, create a mesh and roughly follow the tree shape.





Unwrap your mesh, open the UV/Image editor and put the UV map over the tree image. Give your mesh a material with the image tree as Image Texture. Use the Image Texture Alpha socket as a Factor in a Mix Shader that will mix the Image Texture node and a Transparent node, so that the object is transparent.





Select your object in Object mode, go in the Properties panel > Data > Shape Keys, create 2 shapekeys. Go in Edit mode, select the second shapekey, move your object vertices to deform your tree the way you want.





Back in Object mode, keep the second shapekey selected, play with its value to make the tree move. To animate through time, create keyframes: put the cursor over the value and press i. Open the Dopesheet to move the keyframes if necessary.